Smell and Memory
The sense of smell is closely linked with memory, probably more so than any of our other senses. Those with full olfactory function may be able to think of smells that evoke particular memories; the scent of jasmine in blossom conjuring up recollections of childhood vacations, for example. This can often happen spontaneously, with a smell acting as a trigger in recalling a long-forgotten event or experience.
Smell, Emotion, & Science
In addition to being the sense most closely linked to memory, our sense of smell is also highly emotive. The perfume industry is built around this connection, with perfumers developing fragrances that seek to convey a vast array of emotions and feelings; from desire to power and vitality to relaxation.
It is likely that much of our emotional response to smell is governed by association, something which is born by the fact that different people can have completely different perceptions of the same smell. Take perfume for example; one person may find a particular brand ‘powerful’, ‘aromatic’ and ‘heady’, with another describing it as ‘overpowering’, ‘sickly’ and ‘nauseating’. Despite this, however, there are certain smells that all humans find repugnant, largely because they warn us of danger; the smell of smoke, for example, or of rotten food.
As a scent enters the nose, it's first processed by the olfactory bulb. This starts inside the nose and runs along the bottom of the brain. The olfactory bulb is part of the limbic system, which is the emotional center of the brain. Within this emotional center, lives the amygdala, which plays a role in emotional memories, and the hippocampus, which is critical to developing memories.
Due to scent passing through this area of the brain, emotions, memory, and scent become intertwined.
Visual, auditory, and touch information do not pass through these brain areas. This is why smell, more than any other sense, is so successful at triggering emotions and memories. Our sense of smell is instrumental.